None.
The present invention relates generally to the art of paper and document handling for computer controlled printers, document scanners, automatic document feeders and other applications and, more particularly, to apparatus capable of separating single sheets of media such as paper, vellum, transparencies, etc. from a stack thereof.
Automatic document processing apparatus such as scanners and desktop printers typically include a shelf or tray for holding a stack of one or more sheets of documents to be scanned or blank paper or other media to be fed, one sheet at a time, from the stack to the other portions of the document processing apparatus. In typical prior art arrangements a top sheet pusher or driven pick roller having a friction surface is used to engage the uppermost sheet in a horizontally oriented or downwardly inclined stack to strip the top sheet from the stack and move it parallel to the surface of the stack toward an upwardly angled single sheet separator wall. Engagement of the leading edge of the sheet with the surface of the separator wall, which is usually inclined from vertical at approximately 25xc2x0, causes the single sheet to move upwardly to the operative portions of the printer, scanner or other type of document handling equipment. The prior art separator wall employs a flat or planar surface or a plurality of spaced upwardly extending rails which have low friction paper engaging surfaces which occupy a common plane. Typically, the rails are made of Teflon coated steel strips which are costly due to the use of coated metal parts. Other separator wall configurations use plastic surfaces to form the wall which, however, are less reliable than the Teflon coated steel strips in reducing the jam rate of the single sheet separator apparatus.
Angled wall paper separator systems further often include a rubber pad or the equivalent near the center to provide additional restraint to reduce the rate of multi-sheet picks. It is desirable for the rubber pad to cause a small, localized buckle in the sheet being picked; however, a high rate of paper jams occurs with particularly light weight paper which has a tendency for the leading edge of the sheet to curl downwardly upon engagement with the angled wall instead of sliding up the paper path.
It is objective of the present invention to reduce the rate of paper jamming and multi-sheet picks in separators using an angled separator wall.
The present invention therefore provides a single sheet separator wall for a single sheet separator apparatus, said wall having a sheet engaging surface for contacting and guiding the leading edge of a sheet which is moved from the top of a stack of sheets into contact with said surface to guide movement of said sheet in a direction generally parallel to said sheet engaging surface, said surface including inner and outer guide areas which extend in said direction, said outer guide areas arranged to contact side portions of the leading edge of a sheet to curl the sides of the sheet prior to engagement of said leading edge of said sheet with said inner guide area.